Population-Based Assessment of Contact Tracing Operations for Coronavirus Disease 2019 in Pirkanmaa Hospital District, Finland

Abstract

Background The COVID-19 epidemic overwhelmed local contact tracing (CT) efforts in many countries. In Finland, SARS-Cov-2 incidence and mortality were among the lowest in Europe during 2020-2021. We evaluated CT efficiency, effectiveness, and transmission settings. Methods PCR test-positive COVID-19 cases and high-risk contacts in the population-based CT database of Pirkanmaa Hospital District (pop. 540,000) during June 2020–May 2021 were interviewed. Results Altogether 353,926 PCR tests yielded 4,739 (1.3%) confirmed cases (average 14-day case notification rate, 34 per 100,000 population); about 99% of confirmed cases and high-risk contacts were reached by contact tracing team. Of 26,881 high-risk contacts who were placed in quarantine, 2,275 subsequently tested positive (48% of new cases), 825 (17%) had been in quarantine ≥48 h before symptoms, and 3,469 (77%) of locally acquired cases were part of transmission chains with an identified setting. Highest secondary attack rates were seen in households (31%), health care patients (18%), and private functions (10%). Among the 311 hospitalized patients, COVID-19 diagnosis or exposure was known in 273 (88%) before emergency room admission (identified patients). Health care workers had the highest proportion of work-related infections (159 cases, 35%). The source of infection was classifiable in 65% and was most commonly a co-worker (64 cases, 62%). Conclusions Our data demonstrates the role of effective testing and CT implementation during cluster phase of COVID-19 spread. Although half of newly diagnosed cases were already in quarantine, targeted public health measures were needed to control transmission. CT effectiveness during widespread community transmission should be assessed.

Risk of COVID-19 in different groups of healthcare professionals between February 2020 and June 2021 in Finland: a register-based cohort study

“…Of these 6,113 COVID-19 cases, 21% had a known COVID-19 contact at work, but we don't know if the work-related exposure was with a patient, a colleague or some other contact at work, which has been shown to be sources for work-related infection [ 4 , 22 , 23 ]. In contact tracing data from Finland, it was reported that in healthcare settings most COVID-19 transmission took place between colleagues (62%) or from COVID-19 patients before their identification (33%) [ 24 ]. Only in 5% of the cases transmission occurred from a known COVID-19 patient.…”

Risk of venous thromboembolism in COVID‐19 infection

“…During the study period, everyone with respiratory symptoms was advised to be tested with SARS‐CoV NAAT free of charge. More specific testing criteria during the study period were previously described 9 . All venous thromboembolic events of the study patients (ICD‐10 diagnosis codes I26.0, I26.9, I80.0, I80.1, I80.2, I80.29, I80.3, I80.8, I80.9, I82.88 and I82.9) recorded 3 months after the test date in the Tampere University Hospital discharge records were identified.…”

“…More specific testing criteria during the study period were previously described. 9 All venous thromboembolic events of the study patients (ICD-10 diagnosis codes I26.0, I26.9, I80.0, I80.1, I80.2, I80.29, I80.3, I80.8, I80.9, I82.88 and I82.9) recorded 3 months after the test date in the Tampere University Hospital discharge records were identified. Incidences of VTE and pulmonary embolism (PE) were calculated for the whole study population and for persons with positive and negative SARS-CoV-2 test results separately.…”